1. Field of the Invention
The invention relates to a method for operating a drive system for a motor vehicle that has an internal combustion engine, a transmission and an electric drive device.
2. Description of the Related Art
EP 1 714 817 A1 discloses a hybrid double-clutch transmission that is connected to the internal combustion engine and has at least two component transmissions on which different transmission ratios can be respectively selected at the same time. The transmission can be operated by various methods.
In such drive systems, various situations occur in such drive systems in which the internal combustion engine has to be adjusted from its deactivated state to its energized state in which the internal combustion engine drives the drive axle and therefore the wheels of the motor vehicle. The internal combustion engine is deactivated when the motor vehicle is operated exclusively with the electric drive device, or in a coasting mode where the motor vehicle coasts exclusively on the basis of the previously acquired momentum. However, the internal combustion engine must be restarted near the end of the inactive state. This restarting should occur as comfortably as possible, but at the same time also occur dynamically. The rotational speed of the internal combustion engine should be adjusted during the starting process by means of open-loop and/or closed-loop control to a target or rotational speed that is present at the transmission input. Additionally, rotational speed of the internal combustion engine should be adjusted during the starting process should ensure that the motor vehicle does not carry out a change in acceleration that does not correspond to the driver's request. For example, the motor vehicle may coast toward a traffic light that is at red but is switched over to green. Thus, a driver's request may be to achieve the highest possible acceleration from the coasting state. This leads to the requirement that the re-starting of the internal combustion engine should occur as dynamically as possible, i.e. within the shortest possible time.
Furthermore, the rotational speed of the transmission and the shifting elements assigned to the transmission may not be high enough at low speeds of the motor vehicle to start the internal combustion engine in a sufficiently comfortable way. This occurs because a reversal of torque would continuously occur at the shifting elements as a result of the high degree of rotational irregularity of the internal combustion engine.
The object of the invention is to provide a method for operating a drive system for a motor vehicle having an internal combustion engine, a transmission with at least two component transmissions, and an electric drive device. The method is to enable the internal combustion engine to be adjusted from its deactivated state to its energized state in a way that is as comfortable as possible and at the same time as dynamic as possible.